Intense efforts, in research and development are directed toward superconductive oxides for practical use, for example, magnet coils of the nuclear magnetic resonance imaging apparatus, magnet coils of the particle accelerator, the power transmission line and a like use. The present invention relates to a method of producing an oxide superconductor, which exhibits excellent superconductivity and high mechanical strength as compared to the superconductor produced by the prior art method, and an oxide superconductor produced by the method.
Recently, various superconductive oxides with high critical temperatures (Tc) have been discovered. For producing superconducting wires including such superconductive oxides, for example, Y-Ba-Cu oxide, there has been proposed that a powder mixture which includes Y.sub.2 O.sub.3 powder, BaO powder and CuO powder is charged into a metallic pipe, which is then diameter reduced to form a composite wire, which is in turn heat treated for a solid-state reaction so that the superconductive oxide is produced in the core. According to such a method, it is difficult to provide a high forging ratio without breaking of the composite wire. Thus, the core, having an insufficient green density, of the composite wire has a tendency that during heat treatment thereof, solid phase reaction does not take place sufficiently and hence excellent superconductivity is not obtained. Further, when sintered, a core of such an insufficient green density provides a relatively large porosity of superconductor, which is poor in mechanical strength and is liable to produce cracks in it when it is wound around a magnet core, the cracks considerably degrading superconductivity thereof.
Accordingly it is an object of the present invention to provide a method of producing a superconductor, in which the green density of the compact, is raised fairly high as compared to the prior art method, and which thus exhibits excellent superconductivity and high mechanical strength as compared to the superconductor produced by the prior art method.